The disclosure generally relates to an Ethernet communication device and, more particularly, to an Ethernet communication device supporting an auto medium dependent interface (MDI)/medium dependent interface crossover (MDIX) function.
When an Ethernet device is connected by using a twisted pair cable, a straight-through cable is required if a MDI device, such as a network card or a router, is to be connected with a MDIX device, such as a hub or an exchanger. If a MDI device is to be connected with another MDI device or a MDIX device is to be connected with another MDIX device, a cross-over cable is required for the connection. As a result, network managers have to adopt different types of cables depending on the type of devices to be connected, which is troublesome to the network management. Accordingly, some Ethernet devices adopted the auto MDI/MDIX function to automatically detect the type of signal transmitted and received at a transmission port, so as to communicate with another Ethernet communication device correctly.
In a traditional structure supporting the auto MDI/MDIX function, two sets of communication circuits are employed at each of transmission ports to respectively receive a signal transmitted through the straight-through cable and a signal transmitted through the cross-over cable. Afterward, according to the signals received by the two communication circuits, a subsequent stage circuit selects a suitable type of signal to communicate with another Ethernet device. However, this structure requires two sets of communication circuits at each of transmission ports so the hardware structure is more complicated and the circuit area is greater as well. As a result, the circuitry design complexity and hardware cost are both increased.
Accordingly, another traditional approach utilizes only one communication circuit at each of transmission ports, but a plurality of switches are employed between the communication circuit and each of multiple signal pins. The communication circuit can switch to different signal pins via the switches to determine the type of received signal at the transmission port. However, a disadvantage of this approach is that the above switches are connected directly with the signal pins. If the ESD protection level of the selected switch is not robust enough, the signal path between the communication circuit and the signal pin is easily damaged, thereby causing malfunction of the Ethernet device.